Move over Yanny vs. Laurel, the Internet has a new viral illusion – and we’re breaking down how you can do it yourself.

Known as the #HandSwapChallenge, the visual illusion shows a woman who appears to be swapping her hands. First posted by Twitter user kay_dera, the video had more than 3 million views at the time of publication.

Before we get into it, take a look for yourself.

Did you get it? If so, you’re one of the many people who were quick to catch on.

Others, not so much. 

 

We're going to break it down for those of you still scratching your heads. First, extend both hands out and place one with an open palm in front. Next, interlace your second hand from behind. As you pull both hands back towards you, make a fist with your forward hand and extend the fingers of your rear hand out. Add a popping motion forward for dramatic flair. If you're still totally lost, I recorded a nifty how-to below.

The #HandSwapChallenge joins a long list of visual illusions flooding the Internet in recent months, from the blue/gold dress to the shape-shifting golden mug. But how do optical illusions work and what happens in our brains when we see them?

It all comes down to the way our brain interprets what we see. First, our eyes view an object, then the optic nerve sends that visualization to the brain for interpretation. These illusions occur when our brain interprets things based on what we think might happen, rather than what is really happening. At first glance, it appears the hands are swapping, so we interpret it as such. 

“Optical illusions fascinate us, challenging our default notion that what we see is real. They demonstrate that all our perception is [an] illusion, in a sense – incoming sensory information is interpreted, yielding the internal representation of the world,” wrote visual neuroscientist Michael Bach in a 2006 paper. (If you want to waste a few hours today, be sure to check out his online collection of visual illusions).

Visual illusions, particularly those that make the viral rounds, help scientists understand how people perceive events and could even help in understanding referee judgments and eyewitness statements.